> -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Blaicher, Christopher Y. > Sent: 11 April, 2017 21:25 > To: [email protected] > Subject: Re: Paging subsystems in the era of bigass memory > > It has been a while since I worked on DB2, but it is sounding like your > buffer pools are too big. > > Consider this: > DB2 will read a required page into 'new' buffer pool page before it will > invalidate a page it already has in storage. Now we have a physical page > in use. > > The system periodically comes around and looks at the UIC for a page and > if it is high enough, it will page it out. Now we have a page on AUX > storage. > > If DB2 doesn't need the data on that page, or doesn't need to use that > page for a different data page, then that page just hangs out on AUX > storage. >
From here, there the story still goes on IIRC: if DB2 again needs the data, it would be paged in in any normal task. However, DB2 is more intelligent: it keeps track of how long it takes to page-in the page or read it again from disk, in a I/O that is already running. If the latter is faster this is used and the aux slot is really useless. Kees. ******************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. Koninklijke Luchtvaart Maatschappij N.V. (also known as KLM Royal Dutch Airlines) is registered in Amstelveen, The Netherlands, with registered number 33014286 ******************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
